The present invention relates generally to shrink packaging machines and, in particular, to shrink packaging machines for shrink wrapping articles wherein the articles are compressed during the shrink wrapping process.
In shrink wrapping articles, it is common to entirely encase each article, including top and bottom, with a shrink film, such as polyvinyl chloride or polypropylene soft shrink material, and then transport the article covered in shrink film on a mesh conveyor belt through a shrink tunnel. Many times a compressible article has a height that is more than the height allowance of the shrink tunnel through which the article is conveyed. Consequently, such article will need to be compressed in order to fit through the shrink tunnel.
Additionally, and perhaps more importantly, compressing articles during shrink wrapping is valuable in that the resulting shrink wrapped article consumes less space during shipment, during storage in warehouses, and during display on retail shelves. For instance, significant value can be achieved by compressing and shrink wrapping sweatshirts, blankets, pillows, or bedspreads for distribution and sale.
One approach utilizes shrink tunnels having hot air chambers and mesh belt conveyors, wherein a “mesh belt conveyor” is considered to be a conveyor having a belt comprising a mesh material. In this approach, a bottom mesh belt conveyor and a top mesh belt conveyor are synchronized to travel in the same direction at the same speed through a hot air chamber of the shrink tunnel. As the article travels through the tunnel, the top conveyor and bottom conveyor compress the article. Typically, hot air is heated to between 150° Fahrenheit and 600° Fahrenheit and, while the article is conveyed through the hot air chamber, the hot air is blown onto the shrink film between the openings in the mesh material. The hot air blown thereby shrinks the shrink film about the article. While this method is effective for compressing and shrink wrapping the article, the method tends to leave an undesirable mesh pattern in the shrink film surrounding the article. The pattern results because portions of the film that are in contact with the mesh belt conveyor are restrained from shrinking at the same rate as the film that is not in contact with, and thus not restrained by, the mesh belt conveyors.
Another approach includes an arrangement of opposed bottom and top solid belt conveyors synchronized to travel in the same direction through a shrink tunnel at the same speed. Similar to the foregoing approach, as the article travels through the shrink tunnel, the top conveyor and the bottom conveyor compress the article. The shrink packaging in this approach, however, occurs through the direct heating of the belts, rather than the circulation of heated air through openings in a mesh material as described above. Unfortunately, the pressure that the solid belts exert on the article to compress it also inhibits free movement of the shrinking film, which is necessary in order for the film to shrink properly.
Moreover, in the consumer retail context, a compressed and shrink wrapped package is normally not very presentable as a retail package for purchase by a consumer. The wrinkles in the film, visible tunnel belt pattern, and other detractions that normally result from the shrink packaging process serve as significant detractions to display and sale of the shrink wrapped product. High dollar items like bedspreads need to look appealing on retail display; therefore, the quality of the package matters. Accordingly, in order to accomplish the desired space savings while still having a presentable retail package, it is conventional to package the product in a retail package and then shrink wrap the retail package for the space savings during transport and storage. Then, once the shrink wrapped product arrives at the final destination for retail sale, the shrink wrapping is removed and product in its retail package is then put on display. In some cases, the retail package regains its original volume for display.
In view of the foregoing, improvements in shrink packaging are desirable. The present invention is believed to provide one or more such improvements.